Conventionally, a technique for measuring a concentration of a blood constituent noninvasively is well known. For example, JP-A-H05-176917 teaches the following technique. A near infrared light having a wavelength in a range between 780 nm and 1300 nm is irradiated on a human body, and then, an intensity of a transmitted light is measured. Based on the intensity of the transmitted light, a concentration of glucose in the human body is detected.
However, in the above technique, when a pressing force of a part of the human body as a measurement object is changed, the measurement result is changed. Thus, it is difficult to detect the concentration of glucose with high accuracy.
Thus, it is required for a blood constituent concentration detector to detect the blood constituent concentration with high accuracy.
Further, it is considered that an alcohol concentration in blood of a driver of a vehicle is measured, and a starter for a vehicle controls a starting operation of the vehicle based on determination whether the alcohol concentration in blood is smaller than a predetermined reference value.
In the above case, it is also required to detect the alcohol concentration in blood with high accuracy.